1. Field of the Invention
The invention relates to a piston ring which covers a circumferential surface of a piston and in which retaining surfaces of the piston ring engage the top and bottom of the piston.
2. Description of the Related Art
U.S. Patent Application Publication No. US 2002/0043768 discloses a piston ring for covering a circumferential surface of a piston, i.e., a flat piston of a vibration damper. To improve the sealing function, the piston ring disclosed by this reference includes support segments with retaining surfaces in the area of the piston ring joint. However, if there is an unfavorable combination between the tolerance field for the diameter of the piston with the piston ring and the tolerance field of the cylinder of the vibration damper, a leakage gap may form in the area of the joint, which reveals itself as a wide range of variation in the damping forces at very high damping force values. It would, of course, be possible to specify even narrower tolerance fields. However, the piston ring is preferably an injection-molded plastic part and the manufacturing tolerances of the production process determine the limits of the tolerance fields. If the tolerance fields were to be narrowed too much, the production of the piston rings would be associated with a disproportionate increase in the amount of waste.